Tumbleweeds enlisting in the military

When we hear the word tumbleweed we can’t help but think of a Clint Eastwood wannabe riding in on a horse in some Spaghetti Western movie. But the reality is that these symbolic plant skeletons are useful for something other than movie props: soaking up uranium.

By definition, tumbleweeds are the top part of a plant that dethatch from the root once they become mature and dry. Although they come from Russia, they have become a symbol of the American West in the media.

Some people use it for décor, covering them with Christmas decorations or using them to convey a Western theme. But the military has now put these plants to use in a way that is actually, well, useful.

Depleted uranium, a heavy metal that is toxic if ingested, often contaminates military sites where it is used in armor-piercing bullets. Studies have been conducted to find out which plants are best for absorbing this chemical.

The knowledge that plants are useful for absorbing uranium and other chemicals that can be harmful to humans and animals is not new. But earlier studies had been done on wetter lands and the results were not the same for dry places.

Geologist Dana Ulmer-Scholle of the New Mexico Institute of Mining and Technology discovered that tumbleweeds, or Salsola tragus, are one of the best plants for absorbing uranium in dry desert-like habitats.

“There is some use to what we consider noxious weeds,” Ulmer-Scholle said.

Ulmer-Scholle worked with the US Department of Defense to find efficient, low-cost ways to clean up the soil and weapon testing areas and battlefields where depleted uranium had been used.

Tumbleweeds were found to be the fittest for this task in desert areas because they grow quickly without great need for irrigation.

“Our goal is to use plants with the least amount of water and the minimum amount of care,” Ulmer-Scholle said.

Growing tumbleweeds on purpose might sound counterproductive, considering they would become a nuisance one they become detached and begin their trademark tumbling. But it turns out, they absorb uranium the best before they flower and create seeds.

Ulmer-Scholle says the plants can be harvested before they begin to flower. The soil would be clean and nobody has to worry about excess tumbleweeds appearing on the road or spreading seeds.

On Nov. 10, 2004, Ulmer-Scholle presented her findings at the annual meeting of the Geological Society of America in Denver.

Scientists don’t yet know why some plants absorb uranium or other chemicals. Ulmer-Scholle thinks one reason could be that they use it to create pigments.

Uranium does not give off a lot of radioactivity, but it is still a toxic chemical. It is important to find ways to reduce its contamination of the soil. These findings not only benefit the military, but contribute to the preservation of our planet.